In a number of operations it is desirable to convert a flow of material from, for example, a round pipe, to a jet of essentially rectangular cross-sectional configuration. In feeding cylinder and fourdinier type paper machines, traveling belt thickneners and other traveling screens and dewatering surfaces, for example, this is generally true, and a headbox of some type having a rectangular slice opening is used for this purpose.
A similar conversion is desirable in feeding certain types of stationary screening and dewatering apparatus. Application Ser. No. 614,885, filed Sept. 19, 1975 (now abandoned) and assigned to the assignee of this application, discloses apparatus which includes an improved, generally upright dewatering surface of parabolic configuration. As disclosed in the application, material is fed to the dewatering surface from a series of nozzles positioned along the upstream end of the surface.
U.S. Pat. No. 2,996,182 also discloses a stationary screen in which material is flowed across a screen surface to separate liquids and solids. The screen is disclosed as having a circular screening surface and an extension plate onto which a series of pipes direct jets of material tangentially to allow the jets to unite prior to reaching the screen surface.
Of course where a shallow, rectangular slice opening or a plurality of small diameter pipes or nozzles are used to deliver material to a screen or dewatering surface, the danger of a blockage at the slice opening or the outlets from the pipes or nozzles is great, but has been accepted as a necessary disadvantage associated with converting the flow to the desired condition for deposit on or across a screen or dewatering surface.